This invention relates generally to turbomachines and, more particularly, to means for axially retaining blades in a rotary disk thereof.
Retention of aerodynamic blades within the periphery of a turbomachinery rotor disk has long been a problem for the industry. The most common method of retaining blades in the disk is by a combination of dovetailed blades and axial slots in the periphery of the disk. This method has been found quite satisfactory and desirable for purposes of withstanding the radial loads caused by centrifugal force. However, since there are considerable axial forces on the blades, there is a necessity to provide for axial retention thereof in both directions. In this connection, it is desirable to minimize weight, windage, and stress concentrations while providing a retention means which is simple and relatively easy to assemble and disassemble. That is, for maintainability and repair purposes, it must be relatively easy to remove and replace a single blade.
For the purpose of enhancing blade stability, it has become common practice to use interengaging shrouds, either at the midspan or at the tip of adjacent blades. These act to dampen vibration and to prevent blade untwist during loading. However, where the adjacent shrouds interlock so as to interengage in both axial directions, as is usually the case, then a blade may not be simply assembled by the mere axial insertion into the disk slot. It has become common practice to insert a blade into the lower portion of the disk slot and then raise it radially outward to engage the adjacent interlocking shrouds, and then to fix the blade in that position by the use of a spacer which is placed in the slot under the blade dovetail.
A known method for axially retaining the blade in its slot is to form a circumferential groove near one end of the dovetail, align it circumferentially with a groove or pair of grooves on the disk, and place a ring through both the dovetail groove and the disk groove to lock it into its axial position. However, it has been found that such a ring, which by the very nature of its function must be flexible, did not provide the necessary strength requirement for axial blade retention. On the other hand, to replace the ring with individual segments would require additional means for maintaining those segments in position both radially and circumferentially.
It is therefore an object of the present invention to provide an improved axial retention method for a shrouded blade.
Another object of the present invention is the provision for an axial retainer with increased strength capabilities.
Yet another object of the present invention is the provision in a blade retainer apparatus for a segmented retainer element.
Still another object of the present invention is the provision in a retainer apparatus for maintaining positive positioning for a segmented retainer element.
Yet another object of the present invention is the provision for a blade retaining apparatus which is relatively simple, light in weight and easy to assemble.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.